JPS5923971B2 - Method for manufacturing conductive polyolefin resin molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the manufacturing method of a conductive polyolefin resin molded article, and aims to obtain a conductive polyolefin resin molded article with extremely little change in electrical resistance over a wide temperature range. It is something.

Conventionally, conductive poly-9 olefin molded bodies are molded from poly-9 olefin resin, particularly polyethylene resin powder, kneaded with a conductive material such as carbon powder.

Since this molded body has a positive temperature coefficient of electric resistance, it is said to be useful as a resistance element with a self-control function, but when used over a wide range of temperatures, , because the electrical resistance value changes greatly, for example, if the conductive layer of a cable is made of the molded body, the electrical performance of the conductive layer will change due to an increase in the conductor temperature, so it is necessary to constantly apply a constant current in the layer. It cannot be passed through, and therefore, the above-mentioned molded body can only be applied to a narrow temperature range. The present invention is based on research into the relationship between the electrical properties of mixtures of polyethylene powder and various conductive substance powders due to temperature changes. Confirm the dispersibility of the conductive material powder in
The electrical resistance value of a molded body in which a conductive material powder is dispersed microscopically has a positive temperature coefficient, whereas a molded body in which the conductive material powder is dispersed in a macroscopic manner has electrical resistance over a wide temperature range, that is, above the melting point of the polymer. The present invention was achieved by discovering that it is possible to obtain a product with very little change in resistance value and excellent thermal deformation characteristics and mechanical properties.
．． 100 parts by weight of a powdered polyolefin resin mainly composed of high viscosity polyolefin resin powder of 1 or less and 5 to 40 parts by weight of electrically conductive powder are mixed using a powder mixing device. It is characterized in that compression preforming is performed at room temperature while applying a pressure of /Cwi, followed by heat treatment.

When the powdered polyolefin resin used in the method of the present invention is formed using only a high viscosity polyolefin resin powder, a high viscosity polyolefin resin powder having a melt index of 0.03 or less is used. Polyethylene resin powder or crosslinked polyethylene resin powder is preferred. In addition, the average particle size is preferably in the range of 50 to 400μ, and if it is less than 50μ, the electrical resistance value due to temperature changes will be large, and if it exceeds 400μ, compression molding will be difficult and the particles will be difficult to process. The b1 electrical resistance value varies due to non-uniform dispersion. Furthermore, in the method of the present invention, if the matrix is formed only from high viscosity polyolefin resin powder, the strength of the molded product may become brittle, so a small amount of low viscosity polyolefin with a melt index of 0.1 or more is added to the high viscosity polyolefin resin powder. A resin powder may be mixed, and the amount added is preferably 5 to 12 parts by weight of the latter powder per 100 parts by weight of the former powder. The electrically conductive material powder is not particularly limited, and metal powders such as carbon black powder and aluminum powder can be used. In addition, the particle size is 10 to 100
It is desirable that it be about μ. In the method of the present invention, 5 to 4 parts of the electrically conductive substance is added to 100 parts by weight of the high viscosity polyolefin resin.
0 parts by weight, preferably 8 to 20 parts by weight.This mixing method is carried out by uniformly dispersing the powder in advance using a powder mixing device such as a V blender or a Banbury mixer.

The mixture thus obtained is subjected to room temperature compression preforming under a pressure of 300 to 3,600 Kf/Crl, and then heat treated for a short time to obtain a molded article.

The heat treatment is preferably carried out within 20 minutes in a temperature range of 5° C. below the melting point of the polyolefin resin powder to 70° C. above the melting point using a heating device such as an air constant temperature bath or a high frequency bath that can provide uniform temperature distribution. Although it is not possible to clarify the conductive mechanism of the conductive polyolefin molded body obtained by the method of the present invention, it is possible that the specific internal surface formed by the grain boundaries of the polyolefin resin powder is It is thought that it will remain as it is even at high temperatures.

Next, examples of the method of the present invention will be described.

Examples 1 to 4 100 parts by weight of ultra-high molecular weight polyethylene resin powder (M.lO.Ol or less) with a particle size of 200μ was added with conductive carbon black powder (Lion, Akzo Co., Ltd. KETSUCHEN BLACK EC) as shown in Table 1. The mixture was added as shown, processed in a grinding mixer, and then mixed in a V-type blender.

This mixture was filled into a cylinder with a diameter of 24.5T1r1n and pressurized via a piston, and the mixture was preformed to obtain a plate-shaped sample. Furthermore, the plate-shaped sample was placed in an air-controlled oven and heat-treated by applying a load of 450 f perpendicularly to the surface of the sample in order to improve the contact between the surface of the sample and the measurement electrode. A polyolefin resin molded article was obtained. The results of measuring the electrical resistance value and mechanical properties of this molded body are shown in Table 1. Comparative Example 1 Polyethylene resin powder with a particle size of 200μ (M.ll.O)
15 parts by weight of conductive carbon black was added to 100 parts by weight, and mixed thoroughly in a mold blender.

The subsequent steps were performed under exactly the same conditions as in Example 1 to obtain a conductive polyolefin resin molded article. The results of measuring the electrical resistance value and mechanical properties of this molded body are also listed in Table 1. As is clear from the above table, almost no change in electrical resistance was observed over a temperature range above the melting temperature of the polyethylene resin.

Examples 5-6 High-density polyethylene powder with a particle size of 150μ (M.lO.5
) Cross-linked polyethylene powder 1 irradiated with gamma rays in vacuum
15 parts by weight of conductive carbon black powder was added to 00 parts by weight, treated with a pulverizing mixer, and then mixed in a mold blender.

This mixture was uniformly filled into a rectangular mold and pressurized with a hydraulic press to obtain a rectangular sample. Further, the sample was subjected to a heat treatment to obtain a conductive polyolefin resin molded article. The results of measuring the electrical resistance and mechanical properties of this molded body are shown in Table 2. Comparative Example 2 High-density polyethylene powder (M.lO.
5) 15 parts by weight of conductive carbon black was added to 100 parts by weight, kneaded with a heated roll, and then molded with a hot press to obtain a conductive polyolefin resin molded body.

5 The results of measuring the electrical resistance value and mechanical properties of this molded body are also listed in Table 2.

Fat powder (M.I 0.01) 95% by weight and average particle size 15
0μ high density polyethylene resin powder (M.lO.7)5
15 parts by weight of conductive carbon black were added to 100 parts by weight of polyethylene resin powder consisting of
After filling the tablet into a tablet molding machine and preforming, the resulting molded product was heated at 160°C while applying a load of 450f as described above.
A conductive polyethylene resin molded body having a thickness of 71 fr1n was obtained by heat treatment for 15 minutes.

Furthermore, silver paste was evenly applied to both sides of this disk, and 10
The temperature dependence of electrical resistance was measured in an oven while flowing a direct current of mA. The results are shown in Table 3.
As detailed above, according to the method of the present invention, a conductive molded body with almost no change in electrical resistance over a wide temperature range and excellent mechanical properties can be obtained, so it can be used for power cables. It is extremely useful as a conductive layer or other conductive material.

Claims (1)

[Claims] 1. Powdered polyolefin resin 10 mainly composed of high viscosity polyolefin resin powder with a melt index of 0.1 or less
After mixing 0 parts by weight and 5 to 40 parts by weight of electrically conductive powder using a powder mixing device, this mixture was mixed with 300 to 36 parts by weight of electrically conductive powder.
A method for producing a conductive polyolefin resin molded article, which comprises compression preforming at room temperature while applying a pressure of 0.00 kg/cm^2, and then heat treatment. 2. The method for producing a conductive polyolefin resin molded article according to claim 1, wherein the powdered polyolefin resin consists only of a highly viscous polyolefin resin powder having a melt index of 0.03 or less. 3 Powdered polyolefin resin is 5 to 5 parts by weight of low viscosity polyolefin powder per 100 parts by weight of high viscosity polyolefin powder.
The method for producing a conductive polyolefin resin molded article according to claim 1, wherein the mixture contains 12 parts by weight.